This invention relates to a seat apparatus for a vehicle, capable of variably controlling a bearing-surface configuration of a seat.
As a conventional seat apparatus for a vehicle of this kind, there is one disclosed in, for example, Japanese Patent Laid-Open No. SHO 61-257333. In the conventional seat apparatus, a seat is composed of a seat cushion and a seat back. In the seat, a front air mat, a center air mat, a pair of cushion-side air mats, and a pair of back-side air mats are arranged respectively within support sections such as a front support section, a center support section, a pair of side support sections and the like. The arrangement is such that expansion and contraction of each air mat alters a bearing-surface configuration of the seat. In the case where the vehicle operates for a long period of time, each of the air mats is controlled at a constant or predetermined cycle by a timer to alter the configuration of the bearing surface of the seat, so that variation is given to a posture of a passenger together with a lapse of time from the side of the seat, whereby an attempt is made to reduce fatigue.
By the way, various oscillations or vibrations transmitted to a vehicle body are inputted to a passenger seated on the seat, in accordance with running conditions and the like, so that the oscillations generate fatigue in various parts of a human body. Generally, in oscillation of low frequency, motion of the human body is attempted to be restrained to tense muscles, so that each part of the human body is tired or fatigued. In oscillation of high frequency, parts of the human body adjacent to contact surfaces between the seat and the parts of the human body are oscillated so that fatigue is accumulated. Further, oscillation of a certain frequency becomes one of the factors causing the fatigue, because a part of the human body is resonated. Furthermore, the larger the oscillation, the larger the fatigue.
In the conventional seat for the vehicle constructed as described above, however, each of the air mats 105 through 115 is merely controlled cyclicly at constant times set in a timer. Fatigue induced by oscillation transmitted to the passenger is not totally considered. Thus, there is a limit in reduction of the fatigue.